In Usher syndrome, deaf patients also develop retinitis pigmentosa. Usher syndrome type 1B has been associated with mutations in the myosin Vlla gene (MYO7A). In the mammalian eye, myosin VIla protein is located in the cilium of photoreceptor cells and in the apical region of the retinal pigmented epithelial (RPE) cells. Shaker1 mice also carry mutations in the myosin Vlla gene, and several mutant phenotypes have now been identified in the retinas of these mice. The proposed research aims to determine the efficacy of gene therapy for myosin Vlla deficiency in the shaker1 mouse. High titer lentiviruses co-expressing the human myosin Vlla protein and the green fluorescent protein (GFP) will be produced and injected into the sub-retinal space of newborn mice. The efficiency of viral infection and transgene transduction in photoreceptors and RPE cells will be determined by monitoring expression patterns of myosin Vlla and GFP. The rescuing effects of the viral mediated myosin Vlla expression will be determined by assaying previously identified mutant phenotypes in the retinas of shaker1 mice: e.g., the subcellular distribution of the pigment granules in the RPE cells, the distribution of rhodopsin in the photoreceptor connecting cilium, and the phagocytosis of the outer segment disks by the RPE cells. The proposed research will provide data directly relevant to the feasibility of gene therapy for the Usher 1 B syndrome in humans and to the application of lentivirus as a gene therapy vehicle for other inherited retinal diseases.